172 



THE GEOLOGIST. 



feature becomes more prominent in each succeeding escarp- 

 ment; so that in the most southern the strata have been 

 elevated beyond the perpendicular, and turned over, exposing 

 beds many thousand feet below the coal measures. Potts- 

 ville and Mount Carbon are mentioned as good localities for 

 studying these inversions. Beneath every seam of anthracite 

 Mr. Logan detected a bed of fire-clay, containing stigmaria 

 identical in mineral character, and in the mode of occurrence 

 of the fossil plants, with the beds of underclay described by 

 him on a former occasion as occurring under every seam of 

 coal in South Wales. The number of the workable seams 

 in the southern region, Mr. Logan is of opinion, ought to be 

 reduced to one-fifth the amount given by the resident miners, 

 as he allows for repetitions by faults ; but he estimates their 

 aggregate thickness at one hundred feet. The celebrated 

 summit mines, worked in open day, in the neighbourhood of 

 Mauchchunk, presents a nearly solid mass of coal, fifty feet 

 thick. Standing on the edge of the excavation and looking 

 down into the black abyss below, cut out into dark-sided lanes 

 and streets, surrounded by sable precipices, it is impossible 

 (says Mr. Logan) not to be amazed at the store of mineral 

 wealth contained in this one seam, and equal to between 

 40,000 and 50,000 tons of fuel per acre. 



In an appendix to the paper, Mr. Logan gives long and 

 valuable sectional lists ; and, he states, it will be evident from 

 them that he personally examined nearly the whole of the 

 anthracite coal seams noticed in the memoir. 



Nova Scotia. —After his visit to Pennsylvania, Mr. Lo- 

 gan proceeded to Nova Scotia, and investigated the coal- 

 bearing strata in the neighbourhood of Pictou, on the north- 

 ern side of the province (lat. 45^ 48' long., 62° 48' W.) 

 Pictou stands on a carboniferous series, and a bed of coal 

 passes under the town ; but the principal locality for work- 

 able seams is at the Albion Mines, ten miles to the south. 



